OBJECTIVES: Active surveillance (AS) is the preferred approach for low-risk prostate cancer (PCa). Recent efforts have explored new biomarkers to reduce the frequency of surveillance biopsy. This study assessed Stockholm3 for predicting PCa upgrading during surveillance biopsies. MATERIALS AND METHODS: The prospective STHLM3-AS NorDCaP trial included 199 men with International Society of Urological Pathologists grade group 1 (ISUP GG 1) PCa under AS in Sweden, Denmark, and Norway (2019-2022). All men had ISUP GG 1 PCa and received a Stockholm3 test before surveillance biopsies. The primary outcome was ISUP upgrading, defined as ISUP GG 2 or higher. RESULTS: At surveillance biopsy, 72 of the 199 (36%) men were upgraded. Men with upgraded PCa had higher median Stockholm3 (35; interquartile range IQR 26-50) than those without upgrading (23; IQR 14-34, P < 0.01). The area under the receiver operating characteristic curve (AUC) for Stockholm3 was 0.71 (95% confidence interval CI 0.64-0.79). For Stockholm3 ≥15, sensitivity, specificity, and negative-predictive value (NPV) were 0.93 (95% CI 0.85-0.98), 0.26 (95% CI 0.19-0.35), and 0.87 (95% CI 0.72-0.96), respectively, sparing 19% of biopsies while missing five cases (7% of upgrades), none of which were ISUP GG ≥3. At a lower threshold (≥11), sensitivity increased to 0.99 (95% CI 0.93-1.00) with lower specificity (0.11; 95% CI 0.06-0.18) and an NPV of 0.93 (95% CI 0.68-1.00). Prostate-specific antigen density ≥0.15 showed a sensitivity of 0.60 (95% CI 0.48-0.72), specificity of 0.72 (95% CI 0.63-0.80), and NPV of 0.75 (95% CI 0.66-0.83), with an AUC of 0.71 (95% CI 0.63-0.79). Prostate Imaging-Reporting and Data System score ≥3 demonstrated a sensitivity of 0.92 (95% CI 0.83-0.97), specificity of 0.33 (95% CI 0.22-0.44), and NPV of 0.84 (95% CI 0.66-0.95), with an AUC of 0.72 (95% CI 0.65-0.79). CONCLUSION: In men with low-risk PCa under AS, Stockholm3 may enhance risk stratification and reduce unnecessary biopsies. Prostate-specific antigen density and multiparametric magnetic resonance imaging showed comparable performance, with Stockholm3 providing a potentially practical blood-based complement in a multimodal strategy.
Giudici et al. (Wed,) studied this question.